The present invention is concerned with water-insoluble addition copolymers of ethylenically unsaturated amides and other ethylenically unsaturated monomers in which sufficient amide groups are mono-functionally bonded to a polyaldehyde to render the copolymer thermosettable. The copolymer is readily made in the form of a copolymer latex and is useful in processes for the treatment of textile substrates such as binders for nonwoven fabrics and hand or softness modifiers, and in the preparation of papers utilizing binders or coatings.
It is known in the art to employ water-insoluble aldehyde-substituted amide copolymers, in which the aldehyde is a mono-aldehyde, such as formaldehyde, as a binder. Christenson, U.S. Pat. No. 3,037,963, teaches the preparation of mono-aldehyde-substituted amide copolymers, particularly those in which the amide copolymer is a copolymer of acrylamide and the aldehyde is formaldehyde. Kine, et al., in U.S. Pat. No. 3,157,562, teach that certain linear addition copolymers containing N-methylolamide groups and amide groups, in certain proportions, serve as binders for nonwoven fabrics. Steiger et al., in U.S. Pat. No. 3,100,674, teach the use of N-methylolamide copolymers for the stabilization against shrinkage of protein-containing woven and knitted textile materials. In discussing the usable aldehydes, Christenson (U.S. Pat. No. 3,037,963 column 7, line 6) comments "Aldehydes containing two or more aldehyde groups, such as glyoxal, are unsatisfactory and should not be used inasmuch as they cause gel formation when reacted with amide interpolymers." Talet, U.S. Pat. No. 2,886,557, reacts glyoxal with an acrylamide copolymer to produce a crosslinked polymer. We have discovered how to prepare water-insoluble amide copolymers coreacted with polyaldehydes without forming a crosslinked polymer gel. Thus this polymer is useable as a thermosettable binder or treating agent in textile and paper technology. The thermosettable polymer is useful as a self-crosslinking system or, if desired, with external crosslinkers.
Self-crosslinking polymer systems are particularly useful as adhesives in soft fiber fabrics, as the bonding agent to bond a laminate foam to a fabric or a fabric to another fabric, as the bonding agent in nonwoven fabrics, as a fabric backing agent, as a pigment binder especially for use on paper and to bind pigments to glass fabrics, as a pigment binder particularly in pigment printing and dyeing of fabrics, as a fabric finishing agent to modify the hand or weight of a fabric, as a finish for breatheable waterproof colored fabric, as a stabilizer for woolen and worsted fabrics and as a binder for papers. The self-crosslinking nature of the systems produces, upon appropriate curing, products with excellent durability to washing and dry cleaning. The addition of external crosslinking agents is not necessary to produce the appropriate crosslinking although in certain instances it is found useful.
Exposure of workers to formaldehyde has been of growing concern to industry and to regulatory agencies responsible for worker safety. The various formaldehyde amide adducts, such as polymers containing methylolacrylamide, urea formaldehyde resins or crosslinkers and melamine formaldehyde resins or crosslinkers, produce free formaldehyde during curing operations and during storage periods, both before and after curing. One of the purposes of this invention is to replace these binder systems, which produce the toxic formaldehyde particularly during manufacture, by a binder system which is handleable in manufacturing facilities without the necessity for extreme safety precautions. Fabrics utilizing formaldehyde-containing polymers are often found to be irritants, especially when used in contact with sensitive tissues, so a replacement polymer, such as that of the instant invention, is needed.